The present invention relates to xanthine derivatives having anti-dementia activity and being useful as an anti-dementia drug.
Xanthine derivatives have been hitherto known in the prior art. For example, Mol. Pharmacol., 33, 585 (1988) discloses a compound of the formula (A) having adenosine A.sub.1 receptor antagonistic activity. ##STR8##
J. Med. Chem., 31, 745 (1988) discloses a compound of the formula (B) having adenosine A.sub.1 receptor antagonistic activity. ##STR9##
Eur. J. Med. Chem., 25, 653 (1990) discloses xanthine derivatives of the general formula (C): ##STR10## (wherein Q.sup.A represents alkyl) which exhibit bronchodilator activity.
Canadian Patent No. 724173 discloses xanthine derivatives of the general formula (D): ##STR11## (wherein R.sup.A and R.sup.B represent alkyl or aralkyl, and Q.sup.B represents cycloalkyl) which exhibit diuretic activity.
Further, WO 86/01724 discloses an insecticide containing xanthine derivatives of the general formula (E): ##STR12## wherein R.sup.C, R.sup.D and Q.sup.C are substituted or unsubstituted aliphatic or alicyclic hydrocarbon having 1 to 8 carbon atoms (substituents are selected from halogen, alkyl and hydroxy), substituted or unsubstituted aromatic hydrocarbon (substituents are selected from halogen, alkyl and hydroxy), or phenethyl.
EP 203721A (Japanese Published Unexamined Patent Application No. 42986/87) discloses xanthine derivatives of the general formula (F): ##STR13## wherein R.sup.e and R.sup.F represent alkyl or amino-substituted aralkyl, and either R.sup.G or R.sup.H is hydrogen and the other is --Y--Z (wherein Y is alkenylene and Z is carboxyl). The xanthine derivatives have adenosine receptor antagonistic activity.
U.S. Pat. No. 5068236 (Japanese Publishes Unexamined Patent Application No. 173888/91) discloses xanthine derivatives of the formula (G): ##STR14## wherein R.sup.I and R.sup.J are lower alkyl; and R.sup.K and R.sup.L are substituted or unsubstituted alicyclic alkyl, The xanthine derivatives have exhibited diuretic activity, renal protecting activity and vasodilator activity.
EP 415456A (Japanese Publishes Unexamined Patent Application No. 173889/91) discloses xanthine derivatives of the formula (H): ##STR15## where R.sup.M and R.sup.N are lower alkyl; and Q.sup.D represents ##STR16## (wherein V.sup.1 -V.sup.2 is --CH.sub.2 --CH.sub.2 --or --CH.dbd.CH--; Y.sup.A is a single bond or alkylene; and n.sup.a is 0 or 1). The xanthine derivatives have exhibited diuretic activity, renal protecting activity and bronchodilator activity.